Exemplary embodiments of the present invention relate to storage, and more specifically, to data integrity of external storage devices.
External storage (also referred to as a secondary storage device) is any device that temporarily stores information and external storage is generally not permanently fixed inside a computer. A direct access storage device, or DASD, is any secondary storage device which has relatively low access time for all its capacity. The DASD is accessed by a computer system. Historically, IBM® introduced the term to cover three different device types: disk drives, magnetic drums, and data cells. Modern DASD most commonly means but is not limited to large disk arrays utilizing, e.g., RAID (Redundant Array of Independent Disks) schemes. A disk array is a disk storage system which contains multiple disk drives. It is differentiated from a disk enclosure, in that an array has cache memory and advanced functionality, like RAID and virtualization. Components of a typical disk array include disk array controllers, cache memories, disk enclosures, power supplies, etc. Typically a disk array provides increased availability, resiliency and maintainability by using additional, redundant components (controllers, power supplies, fans, etc.), often up to the point when all single points of failure (SPOFs) are eliminated from the design. Typically, disk arrays are divided into categories: network attached storage (NAS) arrays, storage area network (SAN) arrays, and/or storage virtualization as understood by one skilled in the art.
In a computer system with one or more host systems (computers) connected to one or more external storage systems, loss of data integrity for data on external storage devices can occur if the wrong data (data residing at the wrong external storage location) is accidentally updated (“clobbered”). Similarly, loss of data integrity can occur if the correct data is updated at the wrong time.